The present disclosure relates to a pixel circuit, a display device including the pixel circuit, an electronic apparatus including the display device, and a method of driving the pixel circuit (display device).
At present, a display device including a pixel circuit (referred to as “a pixel” as well) having a display element (referred to as “an electrooptic element” as well), and an electronic apparatus including the display device are generally utilized. There is known a display device which uses an electrooptic element in which luminance changes depending on a voltage or a current applied thereto as a display element in a pixel. For example, electrooptic elements that change luminance depending on the voltage applied thereto is typified by the liquid crystal display element. On the other hand, electrooptic elements that change luminance depending on the current applied thereto is typified by the organic electroluminescence element (organic EL element or organic light emitting diode (OLED); hereinafter referred to as “an organic EL element”). An organic EL display device using the latter, the organic EL element, is a so-called self-emission type display device which uses the self-emission electrooptic elements as the display element in pixels.
Incidentally, in the display device using the display element, the system for driving the display device may be either of the passive matrix system and the active matrix system. However, a display device adopting the passive matrix system involves a problem that it may be difficult to realize a large-size and high-definition display device although the structure is simple.
For this reason, in recent years, active development has been carried out on the active matrix system which controls pixel signals supplied to a display element in a pixel by using an active element in the pixel, for example, an transistor such as an insulated gate field-effect transistor (in general, Thin Film Transistor (TFT)) as a switching transistor.
In the existing display devices utilizing the active matrix system, the threshold voltages and mobilities of the transistors for driving display elements may vary due to process variation. In addition, the characteristics of the display elements change with time. Such characteristic variation of the drive transistors, and such characteristic changing of the elements constituting the pixel such as the display elements, exert an influence on the emission luminance. That is to say, if image signals at the same level are supplied to all of the pixels, every pixel should emit light with the same luminance and thus uniformity of the picture should be obtained. However, the characteristic variation in the drive transistors and characteristic changing of the display elements impair the uniformity of the screen. In view of this, for example, Japanese Patent No. 4240059 and Japanese Patent No. 4240068 propose a technique which corrects display nonuniformity caused by factors such as the characteristic variation in the elements constituting the pixel circuits, for example the transistors and display elements, in order to control the emission luminance to be uniform over the entire screen of the display device.